> How do these community versions, like Old School Essentials, differ from using the real BECMI rules?
Not a lot. (though Old School Essentials is based on the earlier Basic/Expert or B/X rules, not BECMI [0])
Generally the biggest change is that almost all OSR games use ascending armor class.
> What would motivate a group to pick up one of these, rather than say a reprint of the Rules Cyclopedia (or using a free digital copy from archive.org)?
Old School Essentials is far more clearly written and easier to use. A lot of thought was put into layout so that all of the relevant rules for a given topic (e.g. the steps involved in character creation, or the dungeon exploration rules) fit on a single two-page spread. Spell descriptions are bullet-pointed in a way that makes it very easy to check their effects at a glance.
You can check out the free version and see for yourself [1].
Edit: Another thing to keep in mind is that when the OSR first started you couldn't get print-on-demand versions of old rule books from Wizards. If you wanted to play with something like BECMI you had to hunt for the box sets or the Rules Cyclopedia on eBay or in Half-Price Books, or get pirated PDFs. OSR games provided an alternative.
Ah, lack of availability makes a lot of sense given these community remakes are now two decades old. Improving the content layout also sounds great. I will check them out, thanks!
Kinda weird to differentiate between B/X and BECMI, considering Companion/Master/Immortals are extensions for higher level characters using the same Basic/Expert rules.
Edit: the distinction still seems pedantic to me, but these helped to understand the differences in the context of OSR:
Not a lot. (though Old School Essentials is based on the earlier Basic/Expert or B/X rules, not BECMI [0]) Generally the biggest change is that almost all OSR games use ascending armor class.
> What would motivate a group to pick up one of these, rather than say a reprint of the Rules Cyclopedia (or using a free digital copy from archive.org)?
Old School Essentials is far more clearly written and easier to use. A lot of thought was put into layout so that all of the relevant rules for a given topic (e.g. the steps involved in character creation, or the dungeon exploration rules) fit on a single two-page spread. Spell descriptions are bullet-pointed in a way that makes it very easy to check their effects at a glance.
You can check out the free version and see for yourself [1].
Edit: Another thing to keep in mind is that when the OSR first started you couldn't get print-on-demand versions of old rule books from Wizards. If you wanted to play with something like BECMI you had to hunt for the box sets or the Rules Cyclopedia on eBay or in Half-Price Books, or get pirated PDFs. OSR games provided an alternative.
[0]: https://www.reddit.com/r/osr/comments/evax7d/bx_vs_becmi/
[1]: https://necroticgnome.com/products/old-school-essentials-bas...