This can be configured using VirtualBox or using Qemu. These are the steps required to setup JunOS on GNS3 using Qemu:
Acquire an image of JUNOS. The image file should be with the extension .img
Open GNS3 and go to Edit -> Preferences -> Qemu
Make sure the settings in the General Settings section are correct. Below is a screenshot of what the Qemu settings should look like:
Click on Test Settings to check if your settings are correct
Click on the JunOS tab on the same Preferences window
Enter any name for the identifier name
For the binary image, select the image you acquired in step 1
Select a value for the RAM. The minimum I have seen for this is 256MB. You may also leave this blank and GNS3 will assign this for you.
Enter the number of NICs that you want on the Juniper Router (default is 6)
Select the model of the NICs you want on the Juniper Router (default is e1000)
Sample Settings for JunOS settings section:
Click Save to save the JunOS image. Close the Preferences window by clicking Apply.
Now you are able drag the Juniper Router from the left panel and drop them to the topology.
Note: If you want ta add multiple Juniper routers to your topology, you have to make multiple copies of the image acquired in step 1. Then from the GNS3 program right click on every Juniper router -> Configure -> In the JunOS Image: setting, specify the path of a different image file for each instance.
You can do a PIX emulation if you need to, and there is still a demand for this functionality in spite of there no longer being "official" support for PIX within GNS3.
Best Answer
No. GNS3 is limited to Cisco devices due to being based on Dynamips.