Not necessarily. But let's look at one specific instance of adapting to a different "KBI", as you call it. I picked HAVE_VFS_ITERATE, just because it sounded interesting. What's the story?

Well, in May 2013, Al Viro committed code to Linux to add several new "KBIs", dir_emit and related functions (in include/linux/fs.h, which does not have a license block):

    commit 5f99f4e79abc64ed9d93a4b0158b21c64ff7f478
    Author:     Al Viro <[email protected]>
    AuthorDate: Wed May 15 20:23:06 2013 -0400
    Commit:     Al Viro <[email protected]>
    CommitDate: Sat Jun 29 12:46:48 2013 +0400

    [readdir] switch dcache_readdir() users to ->iterate()
    
    new helpers - dir_emit_dot(file, ctx, dentry), dir_emit_dotdot(file, ctx),
    dir_emit_dots(file, ctx).
    
    Signed-off-by: Al Viro <[email protected]>
    ...
    +static inline bool dir_emit(struct dir_context *ctx,
    +                           const char *name, int namelen,
    +                           u64 ino, unsigned type)
    +{
    +       return ctx->actor(ctx, name, namelen, ctx->pos, ino, type) == 0;
    +}
    +static inline bool dir_emit_dot(struct file *file, struct dir_context *ctx)
    +{
    +       return ctx->actor(ctx, ".", 1, ctx->pos,
    +                         file->f_path.dentry->d_inode->i_ino, DT_DIR) == 0;
    +}
    +static inline bool dir_emit_dotdot(struct file *file, struct dir_context *ctx)
    +{
    +       return ctx->actor(ctx, "..", 2, ctx->pos,
    +                         parent_ino(file->f_path.dentry), DT_DIR) == 0;
    +}
    +static inline bool dir_emit_dots(struct file *file, struct dir_context *ctx)
    +{
    +       if (ctx->pos == 0) {
    +               if (!dir_emit_dot(file, ctx))
    +                       return false;
    +               ctx->pos = 1;
    +       }
    +       if (ctx->pos == 1) {
    +               if (!dir_emit_dotdot(file, ctx))
    +                       return false;
    +               ctx->pos = 2;
    +       }
    +       return true;
    +}

Soon after, this was added in zfsonlinux/zfs.git in include/sys/zpl.h (which has a CDDL license block), gated by HAVE_VFS_ITERATE:

    commit 0f37d0c8bed442dd0d2c1b1dddd68653fa6eec66
    Author:     Richard Yao <[email protected]>
    AuthorDate: Wed Aug 7 08:53:45 2013 -0400
    Commit:     Brian Behlendorf <[email protected]>
    CommitDate: Thu Aug 15 16:19:07 2013 -0700

        Linux 3.11 compat: fops->iterate()
    ...
        Compatibility with older kernels was accomplished by adding
        versions of the trivial dir_emit* helper functions.
    ...
    +static inline bool
    +dir_emit(struct dir_context *ctx, const char *name, int namelen,
    +    uint64_t ino, unsigned type)
    +{
    +       return ctx->actor(ctx->dirent, name, namelen, ctx->pos, ino, type) == 0;
    +}
    +
    +static inline bool
    +dir_emit_dot(struct file *file, struct dir_context *ctx)
    +{
    +       return ctx->actor(ctx->dirent, ".", 1, ctx->pos,
    +           file->f_path.dentry->d_inode->i_ino, DT_DIR) == 0;
    +}
    +
    +static inline bool
    +dir_emit_dotdot(struct file *file, struct dir_context *ctx)
    +{
    +       return ctx->actor(ctx->dirent, "..", 2, ctx->pos,
    +           parent_ino(file->f_path.dentry), DT_DIR) == 0;
    +}
    +
    +static inline bool
    +dir_emit_dots(struct file *file, struct dir_context *ctx)
    +{
    +       if (ctx->pos == 0) {
    +               if (!dir_emit_dot(file, ctx))
    +                       return false;
    +               ctx->pos = 1;
    +       }
    +       if (ctx->pos == 1) {
    +               if (!dir_emit_dotdot(file, ctx))
    +                       return false;
    +               ctx->pos = 2;
    +       }
    +       return true;
    +}

Except that Richard Yao took care to say he felt the copying was "trivial", I don't think this example inspires much confidence that zfs.ko is not a derived work of some GPL software.