I've heard people claim this but never seen any actual evidence of license violations.

Everything seems perfectly in order with both the Linux-based firmware on the X1C[0] and their slicer[1] which is a fork of Prusaslicer.

[0] https://wiki.bambulab.com/en/knowledge-sharing/open-source-s...

[1] https://github.com/bambulab/BambuStudio