SQL Server 2019

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with view_myView as (
SELECT * FROM (VALUES (cast('2020-01-02' as date), 'prg1'),(cast('2020-01-05' as date), 'prg1'),(cast('2020-02-02' as date), 'prg1'),(cast('2020-03-02' as date), 'prg1'),
(cast('2020-01-02' as date), 'prg1'),(cast('2020-01-05' as date), 'prg1'),(cast('2020-02-02' as date), 'prg1'),(cast('2020-03-02' as date), 'prg1'),
(cast('2020-04-02' as date), 'prg1'),(cast('2020-05-05' as date), 'prg1'),(cast('2020-06-02' as date), 'prg1'),(cast('2020-07-02' as date), 'prg1'),
(cast('2020-08-02' as date), 'prg1'),(cast('2020-09-05' as date), 'prg1'),(cast('2020-10-02' as date), 'prg1'),(cast('2020-11-02' as date), 'prg1'),
(cast('2020-12-02' as date), 'prg1'),(cast('2020-12-05' as date), 'prg1'),(cast('2020-12-02' as date), 'prg1'),(cast('2020-12-02' as date), 'prg1'),
(cast('2020-01-02' as date), 'prg2'),(cast('2020-01-05' as date), 'prg2'),(cast('2020-02-02' as date), 'prg2'),(cast('2020-03-02' as date), 'prg2')) AS MyTable([date], software)
)

select 
	software
	,miesiac
	,NewUsers
	,sum(newusers) over (partition by software order by miesiac) TotalUser 
from (select 
		software
		,CONVERT(VARCHAR(7), [Date], 111) miesiac
		, count(*) NewUsers 
	from 
		view_myView
	group by 
		software
		,CONVERT(VARCHAR(7), [Date], 111)
) u
order by 1,2

software	miesiac	NewUsers	TotalUser
prg1	2020/01	4	4
prg1	2020/02	2	6
prg1	2020/03	2	8
prg1	2020/04	1	9
prg1	2020/05	1	10
prg1	2020/06	1	11
prg1	2020/07	1	12
prg1	2020/08	1	13
prg1	2020/09	1	14
prg1	2020/10	1	15
prg1	2020/11	1	16
prg1	2020/12	4	20
prg2	2020/01	2	2
prg2	2020/02	1	3
prg2	2020/03	1	4