It's a GROM DSR.. TI BASIC, Editor/Assembler... anything written in GPL can usually pull DSRs from both ROM and GROM. Most assembly language programs only check ROM DSRs, though.
You can't use ROM DSRs on the cartridge port, unfortunately.
Yea this has been my complaint about Assembly access to DSR's as MIller Graphics has a DSR that finds the same ones as XB or BASIC or EA Cart, but Assembly people like Bruce Harrison never used the Miller Graphics one.
Utill I called him and explained several times why it was better then the normal one he used that would only work on >4000 space alone.
After that he started many programs examples on using GPLDSR LINKS.