The name of the former card is 'Turtwig', and the name of the latter is 'Turtwig GL', so yes, you can have 4 of one and 2 of the other (in fact, up to four of each). This also applies to any other cards owned by trainers, such as the Gym Challenge/Heroes cards, Magma/Aqua/Team Rocket Returns, and the Platinum arc of SPs, since their names are different than normal. This also applies to Pokemon-ex, but not Pokemon Lv. X (for deck construction they count as their previous form).