Among other things, a lack of copyright completely dismantles the proprietary software model, and if you can't sell licenses to proprietary software then you don't have as strong of an incentive to keep the source code proprietary.
No it doesn't. What you're calling licenses (what are often called "End User License Agreements") are not licenses – they are contracts. Licenses give rights that the law otherwise denies (e.g. the right to distribute copies of a copyrighted work or the right to drive on public roadways). The GNU GPL is a license – specifically, it is a copyright license that gives the licensee rights (reproduction of copies, preparation of derivative works, distribution of copies, etc.) that otherwise are exclusively owned by the copyright holder. Contracts on the other hand are agreements between parties in which one or both parties might give up some otherwise legally-granted rights (e.g. the right to pay an employee very small wages). "End User License Agreements" are contracts in which the user agrees to give up rights such as the right to reverse engineer a program or the right to use more than five Microsoft Windows XP systems on one's home network.
I know of no law that forbids the use of software without authorization. It is not an infringement of copyright law to run a program, period. No license is necessary to use any software, free or proprietary (which is why copyright licenses like the GNU GPL come into play only when modifying or distributing so-licensed programs, not when running them). "End User License Agreements" (or "End User Contracts" as I prefer to call them) have little to nothing to do with copyright law and give the agreeing party (the user) no rights to copyrighted software.
Even if copyright law were abolished, these contracts would still apply (unless contract law were also abolished, which would be a bad thing). Users would still be forbidden from studying, modifying, and sharing proprietary programs. Abolition of copyright law would have absolutely no effect on proprietary software, except that non-free programs could swallow up many previously free programs due to the absence of copyleft licenses. Without the advent of either "copyleft contracts" or a law that requires distribution of software in source form, abolition of copyright law would instead be a strong and dangerous blow to free software.
Re: You?
No it doesn't. What you're calling licenses (what are often called "End User License Agreements") are not licenses – they are contracts. Licenses give rights that the law otherwise denies (e.g. the right to distribute copies of a copyrighted work or the right to drive on public roadways). The GNU GPL is a license – specifically, it is a copyright license that gives the licensee rights (reproduction of copies, preparation of derivative works, distribution of copies, etc.) that otherwise are exclusively owned by the copyright holder. Contracts on the other hand are agreements between parties in which one or both parties might give up some otherwise legally-granted rights (e.g. the right to pay an employee very small wages). "End User License Agreements" are contracts in which the user agrees to give up rights such as the right to reverse engineer a program or the right to use more than five Microsoft Windows XP systems on one's home network.
I know of no law that forbids the use of software without authorization. It is not an infringement of copyright law to run a program, period. No license is necessary to use any software, free or proprietary (which is why copyright licenses like the GNU GPL come into play only when modifying or distributing so-licensed programs, not when running them). "End User License Agreements" (or "End User Contracts" as I prefer to call them) have little to nothing to do with copyright law and give the agreeing party (the user) no rights to copyrighted software.
Even if copyright law were abolished, these contracts would still apply (unless contract law were also abolished, which would be a bad thing). Users would still be forbidden from studying, modifying, and sharing proprietary programs. Abolition of copyright law would have absolutely no effect on proprietary software, except that non-free programs could swallow up many previously free programs due to the absence of copyleft licenses. Without the advent of either "copyleft contracts" or a law that requires distribution of software in source form, abolition of copyright law would instead be a strong and dangerous blow to free software.