I know of at least three different software releases/versions:
EarthSiege 2 r1.0 (intl), ISO download, MD5 sums of content
EarthSiege 2 r1.11 (intl), ISO download, MD5 sums of content
EarthSiege 2 r1.11 (German re-release with German user manual PDF by Pointsoft and without the other game demos on the international CD), RAR download, MD5 sums of content
Of numbers 1 and 2 I have uploaded the ISOs to Mega.co.nz, of number 3 only a RAR as I don't have the original ISO anymore.
Many people, including me, consider EarthSiege 2 as abandonware, as it's nearing the 18th year of publishment, with no noticeable marketing/sales since at least ten years. Please do note that the copyright still is with SIERRA ONLINE ENTERTAINMENT and/or their successors/studios.
monodrv capture driver and userland grabber: Source code (github), binary archive