Legend of Grimrock was patterned on Eye of the Beholder, which is available on some abandonware sites. The biggest change (other than the fantastic graphics) is that all the AD&D baggage was thrown out, perhaps because of licensing costs. So no alignments, no sleeping to learn spells, no elves, dwarves, etc. Works for me.
On the next beta...? Sensible not to rush it. The point isn't to produce something quickly that's buggy, but to produce something that's rebalanced with more features. The bugs will appear anyway. No reason to increase them dramatically.