denver and OpenServer are not “two different programs” this is a W M M P-stack — a set of programs in which A means Apache web server, and M is MySql DBMS.
Both Apache and MySql can bind to a pair of ip-address: port - (say - 127.0.0.1:80 and, by default for MySql - 127.0.0.1 mor306). The address / port combination must be unique for each process. Only one process can occupy the full address 127.0.0.1:80 at a time. Otherwise, the processes would not know which process the message came to.
Therefore - if for some reason you want to start two web server processes and two database processes, they must be located on different port / address pairs. Those. you will have to make sure in the OpenServer / Apache and Denver / Apache configs (and, accordingly, MySql) that they are bound to unique ip addresses.
Another thing, I suspect that you do not want to deploy multiple web servers at all, but rather to deploy several sites.
To do this, you only need one web server process (OpenServer or Denver is not important) google "Apache virtual host setting", in the case of database it may be more difficult. If your programs do not affect neighboring databases, but work only with their own database, you do not need an extra MySql process, but if they freely create heaps of databases, they may stop working due to database conflicts or accidentally delete current databases . Such systems are rare, but quite possible (as an example - Phabricator)