Lasergrbl doesn’t have any of the more complex functionality that Glowforge is promising. Camera based alignment, pass through support, double sided cutting etc. As @mad_macs says, re-implementing that functionality after losing access to the GF cloud software would take a long time.
Those features are more advanced than anything previously offered by any commercial manufacturer of consumer lasers. Even Glowforge with their stacks of money and PhDs haven’t been able to make them work after more than two years of development.
We are also relying on access to replacement tubes and other laser hardware. Not having access to compatible tubes would certainly put a damper on any DIY efforts to replace the software.