We’ve been meaning to check out DesignSpark.
Free from practical constraints on board size, pin counts, layers and output types… Multi-page schematic designs are supported…. supports the importing of Eagle design files and libraries…
It’s not open source, but it could potentially be a favorable closed-ware alternative to Eagle. Eagles’s board size limits don’t usually effect us because we use all SMD parts, and the layer limit is pretty moot because 4layer boards are too expensive for us to prototype.
Multiple sheets is a very attractive feature though. Eagle currently limits you to one sheet, which makes big designs unwieldy. Eagle’s big lock-in seems to be the huge number of user generated part libraries.
For an open alternative, there’s Kicad. We haven’t tried it for a few years, anyone know if it’s been updated?