Executive Director

rachel@numfocus.org

Rachel Kerestes joined NumFOCUS in 2025. Trained in both the natural and social sciences, her career spans strategy, advocacy, management and communications. She has served as Executive Director for two national nonprofit organizations and held senior leadership roles in industry associations and consultancies. Her past clients include Fortune 50 companies, universities, foreign embassies, leading consumer brands and innovative start‑ups.

Chief Community Officer

jim@numfocus.org

Jim Weiss joined NumFOCUS in 2017, bringing over seven years of event management experience to the organization. Prior to joining NumFOCUS, Jim worked in Washington, D.C., coordinating congressional hearings for the U.S. House of Representatives and managing events for the U.S. Air Force. Jim hails from Pennsylvania and graduated from Lafayette College.

Chief Finance & Operations Officer

michael@numfocus.org

Michael Savelli joined NumFOCUS in 2026 as Chief Financial and Operations Officer. A mission-driven nonprofit executive, his career spans finance, operations, governance, and organizational transformation across scientific, professional, and membership-based organizations. Michael lives in Alexandria, Virginia with his wife Sharon and enjoys daily visits to his yard from white-tailed deer, foxes, raccoons, and other urban wildlife.

Director of Project Advocacy

arliss@numfocus.org

Arliss Collins joined NumFOCUS in 2020 as the Open Source Developer Advocate. Before joining NumFOCUS, she worked as the Data & Metrics Analyst for the Mozilla Foundation as well as the Participation Coordinator for the Mozilla Science Lab. She brings with her experience in open source advocacy, data science, and community engagement. Arliss has a degree in Engineering from Queen’s University, Canada

Director of Operations

nicole@numfocus.org

Nicole joined NumFOCUS in 2019 as Executive Operations Administrator. Before joining NumFOCUS, she worked as an Executive Coordinator and an Administrative Manager. Nicole has a variety of experiences, including client services, vendor management, project management, accounting, and legal compliance.

Senior Director of Development

marc@numfocus.org

Marc joined NumFOCUS in 2025, bringing over 20 years of experience in sales and marketing with global U.S. companies in Europe, and more than a decade of nonprofit leadership in fundraising and project management across France and internationally. He also brings a unique dual-cultural perspective and a strong track record in fundraising and development on both sides of the Atlantic.

Senior Events Manager

tomara@numfocus.org | events@pydata.org

Community Manager

kari@numfocus.org

Kari joined NumFOCUS in 2024 as an Advocacy Coordinator. She has worked in higher education and the non-profit sector for over a decade. Kari graduated from Augustana University with a Bachelor of Arts degree and from Hawai’i Pacific University with a Master of Arts degree. She is a Ph.D. candidate and lives in the beautiful Black Hills of South Dakota. Kari is a lifelong learner and enjoys working with people, research, and data. In her free time she enjoys cooking and exploring the forest with her husband, two boys, and their Irish Setters.

Operations Manager

claudia@numfocus.org

Claudia joined NumFOCUS in March 2024. Before joining the team, she worked in education as a teacher and in school administration. She’s a graduate of Texas State University and helps with the internal operations of NumFOCUS.

Grants Manager

erin@numfocus.org

Project Resource Mobilization Lead

mk@numfocus.org

MK joined NumFOCUS in July 2024 as the Project Resource Mobilization Lead. With eight years of experience in business development, proposal management, social impact, and nonprofit organizational capacity building, he is excited to contribute to the growing NumFOCUS fundraising team. In addition to his role at NumFOCUS, MK is a certified fitness coach, teaching group fitness in the Washington, DC metro area. He holds a B.A. in Political Science from Sam Houston State University and an M.A. in Sustainable Development, International Policy, and Management from the SIT Graduate Institute.

Internal Finance Specialist

chervonne@numfocus.org

Chervonne Rogers joined NumFOCUS in November 2023 as the Bookkeeper. Chervonne has 20+ years of experience in the accounting field and has worked in different fields within operations, finance, and accounting in several industries. Chervonne has a Bachelor of Science in Business Administration with a concentration in Accounting from Regent University in VA and 15+ years of experience directly in bookkeeping. As much as she loves to work, she also loves being a sports mom and a fur-baby mom.

Project Finance Specialist

savannah@numfocus.org

Prior to joining NumFOCUS in October 2022, Savannah managed multiple clients for a bookkeeping firm. Savannah has a Bachelor of Science in Business Administration from Eastern Oregon University along with multiple years of bookkeeping experience. Savannah enjoys working with numbers and in her spare she likes to spend time with her dogs.

Digital Marketing Specialist

kelby@numfocus.org | social@numfocus.org

Kelby joined NumFOCUS in 2023 as the Digital Marketing Specialist. With nearly a decade of experience in marketing, advertising, PR, and user experience, he is excited to be part of the NumFOCUS team! In addition to his work here, he also supports his community theatre with its marketing needs and is a freelance photographer. He has a B.A. in Advertising and Public Relations from Lindenwood University and an M.A. in Communication from Drury University.