Restricting commercial use would disqualify it from being "open source" according to the OSI's definition [1]. If you changed the text of the GNU GPL, the license proposed by the GGP, you would also no longer be able to call it the GPL since the text of the license itself is copyrighted and not free to edit (to, e.g., prevent fragmentation) [2]. If you did all that the source release could well be a net negative for whatever goodwill the FOSS community has for your company.

What they could do instead is dual-license it under a strong copyleft license like the AGPL 3.0 and a proprietary license betting on companies being reluctant to share their source code. Still, it would hardly be to their advantage at all.

[1] http://opensource.org/osd-annotated

[2] https://www.gnu.org/licenses/gpl-faq.html#ModifyGPL.

Edit: clarified how the GPL can be changed.