# Question about license

**URL:** <https://discourse.slicer.org/t/question-about-license/17668>\
**Category:** Development\
**Created:** [May 18, 2021, 4:51am UTC](https://discourse.slicer.org/t/question-about-license/17668 "2021-05-18T04:51:05Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![GRChoi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/grchoi/32/10973_2.png) [@GRChoi](https://discourse.slicer.org/u/GRChoi)\
**Post date:** [May 18, 2021, 4:51am UTC](https://discourse.slicer.org/t/question-about-license/17668/1 "2021-05-18T04:51:05Z")

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Hi everyone,  
I am interested in building Slicer in Windows.  
I read build instruction and I found something weird.  
Slicer build requires QT 5, and QT is (L)GPL license.  
As I know, (L)GPL is infectious which makes referencing projects (L)GPL license projects, but Slicer is BSD license.  
How is it possible?

Thanks for your help. 🙂

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [May 18, 2021, 4:56am UTC](https://discourse.slicer.org/t/question-about-license/17668/2 "2021-05-18T04:56:25Z")

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GPL is viral, but LGPL is not.

The only restrictions of using Qt with LGPL license are that:

1. you are not allowed to link Qt to Slicer statically
2. if you modify Qt’s source code then you need to contribute back your changes to Qt

None of these are an issue.

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**Author:** ![GRChoi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/grchoi/32/10973_2.png) [@GRChoi](https://discourse.slicer.org/u/GRChoi)\
**Post date:** [May 18, 2021, 5:03am UTC](https://discourse.slicer.org/t/question-about-license/17668/3 "2021-05-18T05:03:18Z")

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Thanks for your reply!