Darkglass said any plugin developer can work with them to port a plugin on the Anagram platform, which means they are opened but they want to control their environement, and I think they are right - they want to make sure everything is stable and the UI is consisent. The size of the screen on the Anagram makes it impossible to display a DAW plugin without development anyway.
The MOD Dwarf was more open, in the sense that a plugin developer could port his plugin for the MOD platform without the help of the MOD team, but there was still no universal plugin loader (plugins had to be ported to the MOD platform).
I liked the Open Source approach of the MOD platform, but the user experience was too techy / geeky (plus the processor wasn't powerful enough). We musicians need a straightforward and streamlined user interface, therefore I think Darkglass has chosen the right approach - as long as they really collaborate with plugin developpers to help them bringing their plugins to Anagram.
Time will tell if Darkglass actually want to open the Platform and make the necessary efforts. I think the more successful Anagram is, the most likely it is that they invest in that direction.
I suppose a lot of guitarists are going to want to use Anagram as well, so Darkglass will have to choose between keeping their pedal focussed on the bass market or open it to the guitar world.