This is AI Claude:

Here are some of the best modern free and open source genealogy software alternatives to Gramps:

Webtrees - A popular web-based genealogy application built with PHP and MySQL. It has features for managing family trees, timelines, reports, and more. Actively developed.
Ancestris - A cross-platform desktop app written in Java. Allows building and analyzing complex family trees. Supports GEDCOM files. Customizable reports and statistics.
GeneWeb - An open source web-based and desktop genealogy software written in OCaml. Feature-rich with collaborative trees, relationship graphs, custom events, and version control.
Family Tree Builder - A Python-based genealogy program focused on ease of use. Integrates with online databases and has tools for DNA comparison. Light-weight.
Nextcloud Genealogy - A genealogy app that integrates with the Nextcloud platform. Manages contacts, family trees, timelines, etc. Web-based, self-hosted option.
Lifelines - A cross-platform desktop app written in Python. Clean interface, lets you record family history information and generate reports. Light-weight.
TreeLine - Another Python-based genealogy app for Linux. Emphasizes data organization and reporting.
Overall, Webtrees, Ancestris, and GeneWeb seem to be among the most full-featured, actively maintained open source Gramps alternatives. The choice depends on your priorities like web vs desktop, DNA integration, etc.