The apostrophe is on the XEQ key of the DM42, or "F". But in RPL, it is not to quote like in Lisp, but to introduce algebraic expressions (although it does quote names as a side effect).
On the simulator / web site, the symbol on the key looks like this: [' ()], it is on the second row on the rightmost column, see https://github.com/c3d/db48x/blob/stable/DB48X-Keys/DB48X-Ke....
The key is labeled like this because it serves a dual purpose to accommodate the smaller number of keys on the DM42 relative to the HP48. It adds a tick when not inside an expression, which in RPL begins an algebraic expression. When you are inside an algebraic expression, then you don't need tick anymore, so the key inserts parentheses inside.
> - Why did he swap the log keys?
Because I personally prefer to have exp and ln rather than ln and log. I also would prefer to have y^x as a primary, unshifted key, and this change is coming soon.
But I recognize that keyboard layout is a personal preference, so I'm currently working on making this customizable. Recently, "User mode" has been introduced, which lets you reconfigure the keyboard the way you want. So if you want to restore decimal LOG as the primary key instead of EXP, then do this: 'LOG10' 24.1 ASN. You should be able to restore EXP to the original position with 'EXP' 25.2 ASN, but there is bug with shifted user keys that I need to fix. This should be fixed in the next release.
In addition, the very next release should offer three layouts:
1) One that is maximally compatible with DM42 / HP42, which I assume is what you want.
2) One that corresponds to the current layout, so that people with existing overlays can keep them.
3) One that corresponds to a new iteration of the key layout that is better suited for DB48x, which is currently being discussed on the HP Museum forum.