(written from a Production point of view)
Round 2 LLC is an American company, founded by entrepreneur Tom Lowe in 2005 and based in South Bend, Indiana, that specializes in model kits, toys and die-cast collectibles. 
In 2007, they purchased the Aluminum Model Toys, Polar Lights and MPC model kit lines from their prior owners, Racing Champions. Round 2 LLC relaunched each of the product lines under their own original brand names, and for the first time in a number of years, all American-licensed Star Trek model kits, marketed since 2007, were being produced by a single company.
Round 2 markets their model kits internationally themselves, and has only once extended an one-time-only sub-license for a limited number of their kits to the Japanese model and kit company Platz, which marketed four kits in 2010 under the combined brand name "AMT/Ertl-Platz" for the Japanese market only on the occasion of the 20th anniversary of Star Trek: The Next Generation's premiere in that market.
The only other company that as of 2020 holds an official license for Star Trek model kits is the German Revell company, which managed to extend the license it held for the Star Trek: Voyager model kit line as well as new products originating from Star Trek: The Original Series and the alternate reality Star Trek films, albeit for the European Union only. The status of the American license of the Voyager model kit line, originally held by the US Revell-Monogram company, is unclear, as no Voyager model kits have been marketed in the North America since 1997, nor are any likely to follow there anytime soon as the last owner of the company declared bankruptcy in June 2018.  Having presumably just simply expired, the American license is likely up for grabs for Round 2, though this would entail the creation of brand new expensive production casting molds as the original ones were turned over to Revell Germany when they renegotiated their license extension around 2007, the same year Round 2 acquired its current holdings. This is something that Round 2 is probably not willing to do in light of the perceived limited appeal of Voyager.
Incidentally, Round 2 also holds the American license for the alternate reality films, and had planned through Polar Lights to start with releases in 2010, but ultimately decided to forego on the line due to the mixed reception of those films by the traditional fanbase. As a result, only the European collectors were provided with a model kit of the alternate reality Enterprise through Revell Germany.
Some Star Trek-related Round 2 brands were exchanged with Tomy, the current owner of Racing Champions (RC2) in 2011.