Firstly, it's important to realize that will be wouldn't be a correct usage. It's either "users are able to..." or "users can..." or, as the author wrote, "users should be able to...".
It's an unusual way of stating the program features, but I can find two very good reasons why the author could have decided to say it like that:
1) The program is open-source. Whether its features work or not depends heavily on how the users test it, report bugs and how often the community upgrades the code. Therefore they are humbly saying that, "this feature is implemented and it should work. We hope it will." Unlike applications or games coded by huge companies for huge amounts of money tested by huge amount of testers where the final product "simply works."
2) The usage may be derived from a change log. They could have added the features on-the-go, presenting them as "we have implemented function X. Now users should be able to open a list of..." If a change log becomes full of such statements, they may be later copied to the features section.
TL;DR: The style is grammatical. It's a humble way of presenting own work. There are alternatives, but it depends on the context what is best to use when.