I'll add in a bit for posterity.
There is no single owner or contact to contact for purchasing the code. The way things work, the contributors have signed a Copyright License Agreement, henceforth called the CLA. This CLA provides the ability of Simple Machines (the Nevada corporation) the ability to use the code as it sees fit and gives it certain legal standing in terms of the code. However, it does not provide for full ownership of the code.
To gain the rights to the older version of SMF, you would need to contact each and every person who contributed unique code to the SMF project and enter into an agreement with them for ownership of that code. That's going to be over 40 people. If even one person refuses to sell that code, you are legally obligated to remove their contributions to the codebase, even if that code was later changed by someone else. If you fail to do so, they have the right to sue you for copyright infringement.
Because of the license on the release version of 2.0 (sometimes called "gold" or "final"), anyone can take that code and use it as a base for their project. They can even sell that code under a full commercial license if they so wish. If you want to "own" SMF, the best option is to use the 2.0 release as a base and make changes on top of it. You can then put whatever license you want on those changes.