Here are some popular VPN server software options:

VPN (Virtual Private Network) server software is used to create a secure and private connection between a client's device and a remote server, often for the purpose of web browsing, file sharing, or other online activities. VPNs are widely used by individuals, organizations, and governments around the world to protect sensitive information and enhance security.

1. OpenVPN: A free and open-source VPN software that allows users to create and manage VPN connections. It supports over HTTP, HTTPS, and IPsec.

2. NordVPN: A free and open-source VPN that supports a wide range of protocols, including HTTP, HTTPS, and TCP/IP. It also offers a free tier for basic usage.

3. BitVPN: A popular VPN that offers both free and paid versions. The free version provides basic features such as creating a VPN account, connecting to a server, and viewing live server content.

4. TortoiseVPN: A free VPN that supports HTTP, HTTPS, and IPsec. It also offers a free tier for basic usage and a paid tier for premium features.

5. PulsarVPN: A free VPN that supports HTTPS and HTTP. It also offers a free tier for basic usage and a paid tier for premium features.

6. Vpnmax: A free VPN that supports HTTPS and HTTP. It also offers a free tier for basic usage and a paid tier for premium features.

7. OpenVPN Free: A free version of OpenVPN that allows users to create and manage VPN connections. It supports over HTTP, HTTPS, and IPsec.

8. VpnGuard: A paid VPN software that offers advanced features such as identity management, multi-factor authentication, and live server monitoring.

9. Netnog: A free VPN that supports HTTPS and HTTP. It also offers an app for mobile devices.

10. Kapwing: A paid VPN software that offers a wide range of features, including identity management, live server monitoring, and user control over their VPN session.

When choosing a VPN server software, it's important to consider factors such as the type of connection you need (e.g., HTTP or HTTPS), the level of security you want, the cost of the service, and the reputation of the VPN provider. Additionally, you should ensure that the VPN you choose is reputable and has been reviews and ratings from trusted sources.