About openBVE
openBVE is intended to be an enhanced remake of BVE Trainsim, or Boso View Express, created by Mr. Mackoy. According to his website, his project started in about 1995 as a simple 8 color graphics train simulator that could only be driven on a straight track (see here). From then on, more and more features were added, the programming language was constantly changed to finally arrive at what would became BVE version 1, which was released to the public in 2000. The game spawned a lot of user-created trains, routes and objects, and all of these components are hand-coded in text files with some effort. The next major release was BVE 2, which is still available today to download in its final version that became available in 2004. The next incarnation, after a lot of waiting, was BVE 4, with version 3 skipped for unknown reasons. BVE 4 extended the possibilities especially regarding train development, and could now use custom written plug-ins in order to simulate safety systems more accurately. However, BVE 4 never was fully backward-compatible with BVE 2, and that is why both versions are still available to download from mackoy's website. As some features were even removed from the game in version 4, some users still prefer playing BVE 2.The last update to BVE 4 was in mid-2005, and now, three years later, the development seems to have come to a hold. The fanbase from all over wrong enjoying the work of Mr. Mackoy so much is not getting any new features now, although there is a strong request for new features. Additionally, users of very recent computer models are getting trouble trying to get BVE to run at all on their systems, because new incarnations of Microsoft Windows are known to break compatibility with older hardware. DirectX especially is a prominent example of an ever-changing programming interface that is not very likely to be supported in all its incompatible versions by graphics card manufacturers anymore.
One major burden in extending BVE with functionality and to get it to run on available hardware is that Mr. Mackoy's program is closed-source software, thus nobody can change the source code to make additions and modifications. openBVE is intended to change that.
First of all, openBVE is a new train simulator that is internally different from BVE, and is engineered from the very beginning to expand the game in easy-to-implement ways. Second, the program is written using .NET, a managed environment for programmers, that has cross-platform capabilities. Also, the open source alternatives OpenGL (Open Graphics Library) for graphics, OpenAL (Open Audio Library) for audio and probably SDL (Simple DirectMedia Layer) for peripheral interfaces are used instead of Microsoft's DirectX. This should easy the portability to even different platforms like Linux. It is intended, but not ensured in this early stage of development.
openBVE seeks to therefore provide these things: An open-source alternative that can be easily edited by anyone (a suitable programmer, that is), forked into other releases, unify the functionality of BVE 2 and BVE 4 into one compatible simulator, and finally to extend the game by new features the community asks for.
You should go on and check out the Features section to learn more about how openBVE works, what benefits it will provide for route and train developers, and what features are definitely intended to be included in the game at some point in time.