That is, a program writen in code or text with parameters such as : square meters, number of floors, wood species, distance travelled.
It looks like open source carbon models are almost unheard of yet.
Building open carbon models isn't difficult, it's the input data that normally require licenses. I have built an open source life cycle assessment (LCA) software which has some traction , and there are alternatives for LCA  and integrated assessment models [3, 4]. However, data availability, especially on the level of completeness and detail you need to answer a specific question like carbon performance of a structure over a given period of time is a challenge. We are working on building a large open database to answer these kinds of questions, and Hacker News readers are welcome. Happy to chat via email if you want more info!
What I'm trying to do is, I believe, complementary to these LCA tools. I'm building a website https://futur.eco that bridges carbon models with our every day life as citizens.
Sorry, it's in french for now, but I have some hopes that you read french :-)
Behind the website is a database of open source and extremely simple LCA models, expressed in a new redable programming language. All of it resides in this single file : https://github.com/laem/futureco-data/blob/master/co2.yaml.
CO2 can penetrate into the concrete and bond with CaO, over time reabsorbing all the CO2 released during the calcination process. In practice, CO2 doesn't penetrate deeply into concrete, so depending on the concrete type and environment something like 25% of the potential absorption of concrete is realized (this is based on a conversation I had with a colleague at work, the number is not exact).