Meromero did actually release the source code for most of Mind Crystal's ASM changes, including the reusable TMs routine - it's all included in the download. There's a post in one of the Mind Crystal threads (either the one here or the Project Pokemon one) that hints at how to use the routines. IIRC to use it you need both a modified version of NSMBe, which is linked in that post, and the "arena offset" which is the RAM address that contains a pointer to the start of HGSS's variable RAM area (which is where the overlay files are loaded to when in use). The latter is very hard to find unless you're familiar with ASM.