You do not need a filter to get a birthday or other list of active volunteers. By default all reports in the Reporter are about active, i.e., not terminated, volunteers. So you can run a volunteer birthday or address list or any of that sort without using a filter to get only active volunteers.
One big exception, however, is Statistics and Hours reports, which will include terminated [inactive] volunteers if they served hours during that period requested.
If by active you mean only those who served hours, but only those who are not terminated, you can make a filter specific to those volunteers.
Open Filters | Add filter | name it Active Served Hours [or whatever works for you] | Save
On the Volunteer Limits tab | scroll way down to Served Hours During | Click it
Click Edit Limitation | type in the specific dates | Save
1. Select Termination Date | click Edit Limitation
Click Is blank [i.e., are not terminated] | Save | Close filters
2. Or, an alternative limitation is:
Active (non-terminated) as of today | click Edit Limitation
Click Yes | Save | Close filters
You can use this filter on any hours based report to exclude those who have served hours but are terminated.
[NOTE: In both (1.) and (2.) limitations above, ignore that the Reporter automatically puts Yes in the 'Include Terminated Volunteers?' field after you set your limitation. It doesn't seem logical, but the Reporter needs to check that part of the database, but it won't include them in this case. [The Yes always has been checked in the background but you couldn't see it and now it's visible. Just ignore it.]